We will determine the extent and the means by which people regulate tetrahydrocannabinol (THC) and other substances absorbed during marijuana smoking. Comparisons between adolescent and adult marijuana smokers, frequent and infrequent users, males and females, those who also use tobacco and nontobacco users will demonstrate the techniques, the limits and the magnitude of dose regulation while smoking marijuana of various potency. Reliable measurement techniques already developed will be applied to the cannabis dosimetry research. Puffing and inhaling patterns, including puff volume measured by flow meter techniques and inhalation volume measured by inductance pneumography, will provide a noninvasive and precise protile of how each cigarette is smoked on a puff by puff basis. Cardiovascular, autonomic, and subjective effects and plasma THC, 11-hydroxy THC, 11-nor-9-carboxy THC and carboxyhemolobin measures will allow determination of relationships between smoking patterns, resulting blood levels and effects. Propranolol induced beta adrenergic blockade and resulting changes in smoking behavior will examine the importance of autonomic system feedback in dose regulation. The health significance of a smokers' dose control is only recently being appreciated by some researchers in tobacco studies. It may be of similar importance to marijuana smokers. Several disciplines, including psychopharmacology, psychophysiology, respiratory physiology, pharmacokinetics and behavioral medicine, are involved. The studies have direct public health implications since, as with any drug, dose is likely to be related to both acute and long term consequences. The relationships between marijuana potency and resulting amounts of material absorbed have been little studied. Only incomplete measures of smoking behavior have been previously used in marijuana research. The detailed examination of marijuana smoking behavior in adolescent smokers may enhance prevention strategies.